Polyphenylene ethers are resins having excellent mechanical and electrical properties and high heat resistance but have the defect of poor moldability and poor solvent resistance. It is therefore under the situation that for utilization of polyphenylene ethers alone, its range is greatly restricted.
On the other hand, polyarylene sulfides represented by polyphenylene sulfide are one of resins classified into heat resistant resins and are known to have, in addition to high temperature tolerability for continuous use and high rigidity, the properties that they have high melt rheology, fire retardant properties and excellent solvent resistance. Polyarylene sulfides have thus been widely used as various molded products or films for practical purpose. However, these polyarylene sulfides are poor in mechanical strength, especially in impact strength. Such a defect is a serious obstacle to broadening the utility to a broader range.
Under the situations, it is a valuable attempt, from an industrial viewpoint, to develop resin compositions with benefit of the properties of each component by blending polyphenylene ethers and polyarylene sulfides each having excellent properties. Indeed, such proposal has already been made (Japanese Patent KOKOKU No. 56-34032). In general, however, since the compatibility between polyphenylene ethers and polyarylene sulfides is low, it is practically difficult to obtain resin compositions having excellent mechanical properties by simply blending the two polymers.
To improve the foregoing problems, there have been proposed the following resin compositions: a resin composition comprising modified polyphenylene ether and polyarylene sulfide (Japanese Patent KOKAI No. 64-36645), a resin composition comprising modified polyphenylene ether, modified polyarylene sulfide and a binder (Japanese Patent KOKAI No. 1-266160), a resin composition comprising modified polyphenylene ether modified by an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride, polyphenylene sulfide and a polyisocyanate compound, or a resin composition comprising polyphenylene ether, polyphenylene sulfide, a modifying agent which is an unsaturated carboxylic acid or an unsaturated carboxylic acid anhydride, and a polyisocyanate compound (Japanese Patent KOKAI No. 2-49023), a resin composition comprising a modified polyphenylene ether modified with an organic compound containing an ethylenic double bond and a carboxyl group or an acid anhydride group, and a polyphenylene sulfide in which free SH terminal group is present in a concentration of 10.times.10.sup.-6 gram equivalents/g or more (Japanese Patent KOKAI No. 3-17153), etc. However, these compositions proposed before are not satisfactory in terms of welding properties in injection- or extrusion-molded products, namely, in terms of the properties of providing molded articles having a minimized rate in decrease of the strength of welded portion to that of non-welded portion, while general mechanical properties or solvent resistance is improved. In addition, either polyphenylene ether or polyarylene sulfide or both should be modified with a carboxylic acid, etc. so that economical disadvantage is involved. Therefore, these compositions are not necessarily satisfactory from an industrial viewpoint.
As compositions which are excellent from an economical standpoint, there are proposed a resin composition comprising a polyphenylene ether, a polyphenylene sulfide and an epoxy resin (Japanese Patent KOKOKU No. 60-11063), a resin composition comprising a polyphenylene ether, a crystalline thermoplastic resin and a compatibilizing agent (Japanese Patent KOKAI No. 63-183954), a polymer blend comprising a polyphenylene ether, a polyarylene sulfide and a compatibilizing agent used for a polyphenylene ether-polyamide polymer mixture (Japanese Patent KOKAI No. 2-36361), a resin composition comprising a polyphenylene sulfide, a polyphenylene ether and a compound containing a specific moiety structure (EP 0368413A2), etc. However, these compositions are not satisfactory in welding properties, either. Furthermore, a resin composition comprising a polyphenylene ether, a polyphenylene sulfide and a polyisocyanate compound is also disclosed in Japanese Patent KOKAI No. 2-49023. However, it is described that the composition has a poor degree of compatibility and, this composition is not excellent in welding properties.